biology - pccua...respiration. • if o 2 is not available to the cell, fermentation, an anaerobic...
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11
Chapter 8Cellular Respiration
Lecture Outline
BiologySylvia S. Mader
Michael Windelspecht
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Outline• 8.1 Overview of Cellular Respiration• 8.2 Outside the Mitochondria:
Glycolysis• 8.3 Outside the Mitochondria:
Fermentation• 8.4 Inside the Mitochondria• 8.5 Metabolism
2
8.1 Cellular Respiration• Cellular respiration is a cellular process that breaks down
nutrient molecules produced by photosynthesizers with the concomitant production of ATP.
• It consumes oxygen and produces carbon dioxide (CO2). Cellular respiration is an aerobic process.
• It usually involves the complete breakdown of glucose to CO2and H2O. Energy is extracted from the glucose molecule:
• Released step-wise
• Allows ATP to be produced efficiently
Oxidation-reduction enzymes include NAD+ and FAD as coenzymes.
3
Cellular Respiration
4
Electrons are removed from substrates and received by oxygen, which combines with H+ to become water.
Glucose is oxidized and O2 is reduced.
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energyglucose
Reduction
Oxidation
6H2O6CO26O2C6H12O6 + ++
Cellular Respiration
5
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O2 and glucose enter cells,which release H2O and CO.
CO2
H2O
Mitochondria useenergy fromglucose to form ATPfrom ADP + P .
ATPADP + P
cristae
intermembranespace
© E. & P. Bauer/zefa/Corbis
6
Cellular Respiration• NAD+ (nicotinamide adenine dinucleotide) A coenzyme of oxidation-reduction, it is:
• Oxidized when it gives up electrons• Reduced when it accepts electrons
Each NAD+ molecule used over and over again
• FAD (flavin adenine dinucleotide) Also a coenzyme of oxidation-reduction Sometimes used instead of NAD+
Accepts two electrons and two hydrogen ions (H+) to become FADH2
Phases of Cellular Respiration
• Cellular respiration includes four phases: Glycolysis is the breakdown of glucose into
two molecules of pyruvate. • It occurs in the cytoplasm.• ATP is formed.• It does not utilize oxygen (anaerobic).
Preparatory (prep) reaction• Both molecules of pyruvate are oxidized and enter
the matrix of the mitochondria.• Electron energy is stored in NADH.• Two carbons are released as CO2 (one from each
pyruvate).
7
Phases of Cellular Respiration Citric acid cycle
• Occurs in the matrix of the mitochondrion and produces NADH and FADH2
• A series of reactions, releases 4 carbons as CO2• Turns twice per glucose molecule (once for each pyruvate)• Produces two immediate ATP molecules per glucose
molecule Electron transport chain (ETC)
• A series of carriers on the cristae of the mitochondria• Extracts energy from NADH and FADH2• Passes electrons from higher to lower energy states • Produces 32 or 34 molecules of ATP by chemiosmosis
8
The Four Phases of Complete Glucose Breakdown
9
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Electron transportchain and
chemiosmosis
Mitochondrion
4 ADP
2
4 ATP total
net gain
2 ATP
Glycolysis
NADH
glucose pyruvate
Cytoplasm
ATP
e–
e–e–e–
e–
2 ATP
The Four Phases of Complete Glucose Breakdown
10
Preparatory reaction
NADH
NADH andFADH2
Electron transportchain and
chemiosmosis
Mitochondrion
2
4 ATP total
net gain
2 ATP
Glycolysis
NADH
glucose pyruvate
Cytoplasm
ATP
e–
e–
e–
2 ATP
e–
e–
e–
4 ADP
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The Four Phases of Complete Glucose Breakdown
11
Mitochondrion
Citric acid cycle
Preparatory reaction
2 ADP 2
NADH
Glycolysis
NADH
glucose pyruvate
Cytoplasm
ATP2
4 ATP total
net gain
2 ATP
ATP
2 ATP
4 ADP
Electron transportchain and
chemiosmosis
NADH andFADH2
e–
e–
e–
e–e–
e–
e–
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The Four Phases of Complete Glucose Breakdown
12
Mitochondrion
Preparatory reaction
2 32 ADPor 34
32or 34
NADH
Glycolysis
NADH
glucose pyruvate
Cytoplasm
ATP
e–
e–
e–
e–
e–
e–
e–
Citric acid cycle
Electron transportchain and
chemiosmosis
NADH andFADH2
2
4 ATP total
net gain
2 ATP
ATP
2 ATP
4 ADP
ATP2 ADP
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8.2 Outside the Mitochondria: Glycolysis
• Glycolysis occurs in cytoplasm outside mitochondria.• It consists of a series of 10 reactions, each with its own
enzyme.• Energy Investment Step:
Two ATP are used to activate glucose. Glucose splits into two G3P molecules.
• Energy Harvesting Step: Oxidation of G3P occurs by removal of electrons and hydrogen
ions. Two electrons and one hydrogen ion are accepted by NAD+
resulting in two NADH. Four ATP are produced by substrate-level phosphorylation.
• An enzyme passes a high-energy phosphate to ADP, making ATP. There is a net gain of two ATP (4 ATP produced - 2 ATP
consumed). Both G3Ps convert to pyruvates. 13
Outside the Mitochondria: Glycolysis
14
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2
2
4
Glycolysisinputs6C glucose2 NAD+
ATP
4 ADP + 4 P
ATP net gain
totalATP
2 ADP
2 NADHpyruvate
outputs2 (3C)
Glycolysis
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G3P glyceraldehyde-3-phosphate
BPG 1,3-bisphosphoglycerate
3PG 3-phosphoglycerate
Energy-investment Step
glucose
Glycolysis
Glycolysis
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G3P glyceraldehyde-3-phosphate
BPG 1,3-bisphosphoglycerate
3PG 3-phosphoglycerate
ADPADP
ATP ATPglucose
Glycolysis
Energy-investment Step
Glycolysis
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G3P glyceraldehyde-3-phosphate
BPG 1,3-bisphosphoglycerate
3PG 3-phosphoglycerate
Two ATP are used to get started.
ADPADP
–2 ATP
Energy-investment Step
ATP ATP
glucose
Glycolysis
Glycolysis
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G3P glyceraldehyde-3-phosphate
BPG 1,3-bisphosphoglycerate
3PG 3-phosphoglycerate
Two ATP are used to get started.
Splitting produces two3-carbon molecules.
G3PG3P
ADPADP
–2 ATP
Energy-investment Step
ATP ATP
glucose
Glycolysis
GlycolysisCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
G3P glyceraldehyde-3-phosphate
BPG 1,3-bisphosphoglycerate
3PG 3-phosphoglycerate
Two ATP are used to get started.
Splitting produces two3-carbon molecules.
Oxidation of G3P occurs asNAD+ receives high-energyelectrons.
Energy-harvesting Steps
NADH NADH
BPG BPG
G3PG3PNAD+NAD+
ADPADP
–2 ATP
Energy-investment Step
ATP ATP
glucose
Glycolysis
E1
GlycolysisCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ADP
G3P glyceraldehyde-3-phosphate
BPG 1,3-bisphosphoglycerate
3PG 3-phosphoglycerate
Two ATP are used to get started.
Splitting produces two3-carbon molecules.
Oxidation of G3P occurs asNAD+ receives high-energyelectrons.
Substrate-level ATP synthesis.
+2 ATP ATP
3PG
Energy-harvesting Steps
NADH NADH
ATP
BPG BPGADP
G3PG3P
NAD+NAD+
ADPADP
–2 ATP
Energy-investment Step
ATP ATP
glucose
Glycolysis
3PG
E2
E1
GlycolysisCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ADP
G3P glyceraldehyde-3-phosphate
BPG 1,3-bisphosphoglycerate
3PG 3-phosphoglycerate
Two ATP are used to get started.
Splitting produces two3-carbon molecules.
Oxidation of G3P occurs asNAD+ receives high-energyelectrons.
Substrate-level ATP synthesis.
Oxidation of 3PG occurs byremoval of water.
+2 ATP ATP
3PG
PEP PEP
Energy-harvesting Steps
NADH NADH
ATP
BPG BPGADP
G3PG3PNAD+NAD+
ADPADP
–2 ATP
Energy-investment Step
ATP ATP
glucose
Glycolysis
3PG
E3
E2
E1
H2O H2O
GlycolysisCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ADP
2
G3P glyceraldehyde-3-phosphate
BPG 1,3-bisphosphoglycerate
3PG 3-phosphoglycerate
Two ATP are used to get started.
Splitting produces two3-carbon molecules.
Oxidation of G3P occurs asNAD+ receives high-energyelectrons.
Substrate-level ATP synthesis.
Oxidation of 3PG occurs byremoval of water.
Substrate-level ATP synthesis.
Two molecules of pyruvateare the end products of glycolysis.
pyruvatepyruvateATP
+2 ATP
(net gain)
ATP
+2 ATP ATP
3PG
PEP PEPADPADP
Energy-harvesting Steps
NADH NADH
ATP
ATP
BPG BPG
ADP
G3PG3P
NAD+NAD+
ADPADP
–2 ATP
Energy-investment Step
ATP ATP
glucose
Glycolysis
3PG
E4
E3
E2
E1
H2O H2O
Substrate-Level ATP Synthesis
23
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enzyme
ADP
ATP
BPG
3PG
8.3 Outside the Mitochondria: Fermentation
• Pyruvate is a pivotal metabolite in cellular respiration.
• If O2 is not available to the cell, fermentation, an anaerobic process, occurs in the cytoplasm. During fermentation, glucose is incompletely
metabolized to lactate, or to CO2 and alcohol (depending on the organism).
• If O2 is available to the cell, pyruvate enters the mitochondria for aerobic respiration. 24
Outside the Mitochondria: Fermentation
• Fermentation is an anaerobic process that reduces pyruvate to either lactate or alcohol and CO2.
• NADH transfers its electrons to pyruvate. • Alcoholic fermentation, carried out by yeasts, produces
carbon dioxide and ethyl alcohol. Used in the production of alcoholic spirits and breads
• Lactic acid fermentation, carried out by certain bacteria and fungi, produces lactic acid (lactate). Used commercially in the production of cheese, yogurt, and
sauerkraut.• Other bacteria produce chemicals anaerobically,
including isopropanol, butyric acid, proprionic acid, and acetic acid.
25
Fermentation
26
2
4
2
glucose
– 2 ATP ATP
E1
G3P
2NAD;
2 NADH
Plants
2CO 2
Animals
2 alcoholor2 lactate
ATP
ATP+ 4
2ADP
E2
BPG4ADP
E3
pyruvate
(net gain)
E4
ATP
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or
Fermentation and Food Production
27
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© McGraw Hill Education./John Thoeming, photographer
Fermentation and Food Production
28© Bruce M. Johnson
Fermentation and Food Production
29© Bruce M. Johnson
Outside the Mitochondria: Fermentation
• Advantages Provides a quick burst of ATP energy for muscular activity.
• When muscles are working vigorously for a short period of time, lactic acid fermentation provides ATP.
• Disadvantages Lactate and alcohol are toxic to cells. Lactate changes pH and causes muscles to fatigue.
• Oxygen debt Yeast die from the alcohol they produce by fermentation.
• Efficiency of Fermentation Two ATP produced per glucose of molecule during fermentation
is equivalent to 14.6 kcal. Complete oxidation of glucose can yield 686 kcal.
• Efficiency is 2.1% of total possible for glucose breakdown. Only 2 ATP per glucose are produced, compared to 36 or 38
ATP molecules per glucose produced by cellular respiration. 30
Outside the Mitochondria: Fermentation
31
Fermentationinputs outputs
2 lactate or2 alcohol and 2 CO2
glucose
2 ADP + 2 P net gainATP2
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8.4 Inside the Mitochondria• The preparatory (prep) reaction
It connects glycolysis to the citric acid cycle.
End product of glycolysis, pyruvate, enters the mitochondrial matrix.
Pyruvate is converted to a 2-carbon acetyl group.
• Attached to Coenzyme A to form acetyl-CoA
• Electrons picked up (as hydrogen atom) by NAD+, producing NADH
• CO2 released and transported out of mitochondria into the cytoplasm
• Occurs twice per glucose molecule32
Inside the Mitochondria
33
2 NAD+ 2 NADH
2 2+ 2 CoA + 2 CO2
2 pyruvate
O OHC
CH3
+ 2 CoA
CoA
CH3pyruvate
carbondioxideacetyl CoA
C OC O
2 acetyl CoA + 2 carbondioxide
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Mitochondrion Structure and Function
34
Inside the Mitochondria
• Citric Acid Cycle Also called the Krebs cycle Occurs in the matrix of mitochondria Begins with the addition of a 2-carbon acetyl group
(from acetyl-CoA) to a 4-carbon molecule (oxaloacetate), forming a 6-carbon molecule (citric acid)
NADH and FADH2 capture energy rich electrons ATP formed by substrate-level phosphorylation Turns twice for one glucose molecule (once for
each pyruvate) Produces 4 CO2, 2 ATP, 6 NADH, and 2 FADH2 per
glucose molecule
35
Citric Acid CycleCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2
e–
e–
1. The cycle begins when a C2 acetyl group carried byCoA combines with a C4molecule to form citrate.
acetyl CoAC2
oxaloacetateC2
CoA
Glycolysis
glucose pyruvatePreparatory reaction
Electron transportchain andchemiosmosis
Matrix
Citric acidcycle
NADH andFADH2
e–
e–
e–
e–
e–
2 ATP
2 ADP
netATP
4 ADP 4 ATP total
2ADP 2 ATP 32ADPor 34
32or 34
ATP
NADHNADH
Citric Acid CycleCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2
e–
e–
1. The cycle begins when a C2 acetyl group carried byCoA combines with a C4molecule to form citrate.
acetyl CoAC2
oxaloacetateC2
citrateC6
CoA
Glycolysis
glucose pyruvatePreparatory reaction
Electron transportchain andchemiosmosis
Matrix
Citric acidcycle
NADHandFADH2
e–
e–
e–
e–
e–
2 ATP
2 ADP
netATP
4 ADP 4 ATP total
2ADP 2 ATP 32ADPor 34
32or 34
ATP
NADHNADH
Citric Acid CycleCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2
e–
e–
2. Twice over, substratesare oxidized as NAD+ isReduced to NADH,and CO2 is released.
1. The cycle begins when a C2 acetyl group carried byCoA combines with a C4molecule to form citrate.
acetyl CoAC2
oxaloacetateC2
citrateC6
NAD
NADH
CoA
ketoglutarateC5
CO2
Glycolysis
glucose pyruvatePreparatory reaction
Electron transportchain andchemiosmosis
Matrix
Citric acidcycle
NADHandFADH2
e–
e–
e–
e–
e–
2 ATP
2 ADP
netATP
4 ADP 4 ATP total
2ADP 2 ATP 32ADPor 34
32or 34
ATP
NADHNADH
Citric Acid Cycle
2
e–
e–
3. ATP is produced as anenergized phosphate istransferred from a substrate to ADP.
2. Twice over, substratesare oxidized as NAD+ isReduced to NADH,and CO2 is released.
1. The cycle begins when a C2 acetyl group carried byCoA combines with a C4molecule to form citrate.
acetyl CoAC2
oxaloacetateC2
citrateC6
NAD
ATP
succinateC4
NADH
CoA
ketoglutarateC5
NAD+
NADHCO2
CO2
Glycolysis
glucose pyruvatePreparatory reaction
Electron transportchain andchemiosmosis
Matrix
Citric acidcycle
NADHandFADH2
e–
e–
e–
e–
e–
2 ATP
2 ADP
netATP
4 ADP 4 ATP total
2ADP 2 ATP 32ADPor 34
32or 34
ATP
NADHNADH
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Citric Acid Cycle
2
e–
e–
3. ATP is produced as anenergized phosphate istransferred from a substrate to ADP.
2. Twice over, substratesare oxidized as NAD+ isReduced to NADH,and CO2 is released.
1. The cycle begins when a C2 acetyl group carried byCoA combines with a C4molecule to form citrate.
4. Again a substrate isoxidized, but this timeFAD is reduced to FADH2
acetyl CoAC2
oxaloacetateC2
citrateC6
NAD
fumarateC4
FADH
ATP
succinateC4
NADH
CoA
ketoglutarateC5
NAD+
NADHCO2
FAD
CO2
Glycolysis
glucose pyruvatePreparatory reaction
Electron transportchain andchemiosmosis
Matrix
Citric acidcycle
NADHandFADH2
e–
e–
e–
e–
e–
2 ATP
2 ADP
netATP
4 ADP 4 ATP total
2ADP 2 ATP 32ADPor 34
32or 34
ATP
NADHNADH
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Citric Acid Cycle
2
e–
e–
3. ATP is produced as anenergized phosphate istransferred from a substrate to ADP.
2. Twice over, substratesare oxidized as NAD+ isReduced to NADH,and CO2 is released.
1. The cycle begins when a C2 acetyl group carried byCoA combines with a C4molecule to form citrate.
5. Once again a substrateis oxidized, and NAD+
is reduced to NADH.
4. Again a substrate isoxidized, but this timeFAD is reduced to FADH2
acetyl CoAC2
NADHoxaloacetate
C2
citrateC6
NAD
fumarateC4
NAD+
FADHATP
succinateC4
Citric acidcycle
NADH
CoA
ketoglutarateC5
NAD+
NADHCO2
FAD
CO2
Glycolysis
glucose pyruvatePreparatory reaction
Electron transportchain andchemiosmosis
Matrix
Citric acidcycle
NADHandFADH2
e–
e–
e–
e–
e–
2 ATP
2 ADP
netATP
4 ADP 4 ATP total
2ADP 2 ATP 32ADPor 34
32or 34
ATP
NADHNADH
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Inside the Mitochondria
42
inputs outputs4 CO2
NADH
FADH22
2 (2c) acetyl groups
6 NAD+
2 FAD
2
Citric acid cycle
P2 ADP +2
6
ATP
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Inside the Mitochondria• Electron Transport Chain (ETC)• Location:
Eukaryotes – cristae of the mitochondria Aerobic prokaryotes – plasma membrane
• Series of carrier molecules: Pass energy-rich electrons successively from one to another Complex arrays of protein and cytochrome
• Proteins with heme groups with central iron atoms
• The electron transport chain: Receives electrons from NADH & FADH2 Produces ATP by oxidative phosphorylation
• Oxygen final electron acceptor: Combines with hydrogen ions to form water
43
Inside the Mitochondria• The fate of the hydrogens Hydrogens from NADH deliver enough energy to
make 3 ATPs. Those from FADH2 have only enough for 2 ATPs. “Spent” hydrogens combine with oxygen.
• Recycling of coenzymes increases efficiency. Once NADH delivers hydrogens, it returns (as NAD+)
to pick up more hydrogens. However, hydrogens must be combined with oxygen
to make water. If O2 is not present, NADH cannot release H+. It is no longer recycled back to NAD+.
44
45
Inside the Mitochondria• The electron transport chain complexes pump H+ from the
matrix into the intermembrane space of the mitochondrion.
• H+ therefore becomes more concentrated in the intermembrane space, creating an electrochemical gradient.
• ATP synthase allows H+ to flow down its gradient.• The flow of H+ drives the synthesis of ATP from ADP and
inorganic phosphate by ATP synthase.• This process is called chemiosmosis.
ATP production is linked to the establishment of the H+ gradient.• ATP moves out of mitochondria and is used for cellular
work. It can be broken down to ADP and inorganic phosphate. These molecules are returned to the mitochondria for more ATP
production.
Organization and Function of the Electron Transport Chain
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2
O212+
2
P
H+
e:
e :
Electron transport chain
high energyelectron
ATPchannelprotein
Intermembranespace
ATPsynthasecomplex
low energyelectron
cytochromeoxidase
cytochrome c
NADH-Qreductase
cytochromereductase
coenzyme Q
NADH
Matrix
FADH2 FAD+
NAD+
2
e-
2 ADP ATP32 ADPor 34
4 ADP
netATP
4 ATP total
2ADP
2ATP
Glycolysis
glucose pyruvatePreparatory reaction Citric acid
cycle
Electron transportchain and
chemiosmosis
NADH andFADH2
NADH
NADHe-
e-
e-e-
e-
e-
32 or34
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+H+H+
H+
H+
H+
ATP ADPH2O
H+
H+
H+
H+
H+
H+
H+
H+
H+H+H+
H+
H+
H+H+
H+
H+ATP
Chemiosmosis
Inside the Mitochondria
• Energy yield from glucose metabolism Net yield per glucose
• From glycolysis – 2 ATP• From citric acid cycle – 2 ATP• From electron transport chain – 32 or 34 ATP
Energy content• Reactant (glucose) 686 kcal• Energy yield (36 ATP) 263 kcal• Efficiency is 39%• Rest of energy from glucose is lost as heat
47
Energy Yield from Glucose Metabolism
48
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glucose
Energy Yield from Glucose Metabolism
49
Cyt
opla
sm
Elec
tron
tran
spor
t cha
in
2net
glucose
2 pyruvate
glycolysis
NADH2 4 or 6
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ATP
ATP
Energy Yield from Glucose Metabolism
50
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Cyt
opla
sm
Elec
tron
tran
spor
t cha
in
2net
glucose
2 pyruvate
2 acetyl CoA
glycolysis
NADH
NADH
2
2
4 or 6
6
ATP
ATP
ATP
Energy Yield from Glucose Metabolism
51
Cyt
opla
sm
Elec
tron
tran
spor
t cha
in
2net
2
glucose
2 pyruvate
2 acetyl CoA
Citric acidcycle
glycolysis
2 CO2
NADH
NADH
NADH
FADH2
2
2
6
2
4 or 6
6
18
4
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ATP
ATP
ATP
ATP
ATP
4CO2
6O2
ATP
6HO2
Energy Yield from Glucose Metabolism
52
Cyt
opla
sm
Elec
tron
tran
spor
t cha
in
2net
2
glucose
2 pyruvate
2 acetyl CoA
subtotal subtotal
glycolysis
NADH
NADH
NADH
2
2
6
2
4 or 6
6
18
4
324or 34
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ATP
ATP
ATP
4CO2
2CO2
FADH2
6O2 6HO2
ATP
ATP
ATP
ATP
ATP
Citric acidcycle
Energy Yield from Glucose Metabolism
53
Cyt
opla
smM
itoch
ondr
ion
Elec
tron
tran
spor
t cha
in
2net
2
glucose
2 pyruvate
2 acetyl CoA
Citric acidcycle
subtotal subtotal
glycolysis
2 CO2
4 CO2
NADH
NADH
NADH
FADH2
2
2
6
2
4 or 6
6
18
4
324
36 or 38total
6 O2 6 H2O
ATP
ATP
ATP
ATP
ATP
ATPATP
ATP
ATPor 34
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8.5 Metabolism• Foods Sources of energy rich molecules
Carbohydrates, fats, and proteins
• Degradative reactions (catabolism) break down molecules. Tend to be exergonic (release energy)
• Synthetic reactions (anabolism) build molecules. Tend to be endergonic (consume energy)
54
The Metabolic Pool Concept
55
ATP
ATPElectrontransportchain
proteins carbohydrates fats
aminoacids
glucose fattyacids
glycerol
acetyl CoA
Glycolysis
pyruvate
ATPCitricacidcycle
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© C Squared Studios/Getty RF
Metabolic Pool • Glucose is broken down in cellular respiration.• Fat breaks down into glycerol and three fatty
acids.• Amino acids break down into carbon chains and
amino groups. Deamination (NH2 removed) occurs in the liver.
• Results in poisonous ammonia (NH3)• Quickly converted to urea
Different R-groups from amino acids are processed differently.
Fragments enter respiratory pathways at many different points.
56
Metabolic Pool• All metabolic compounds are part of the
metabolic pool.• Intermediates from respiratory pathways can be
used for anabolism.• Anabolism (synthetic reactions of metabolism): Carbohydrates
• Start with acetyl-CoA• Basically reverses glycolysis (but different pathway)
Fats• G3P converted to glycerol• Acetyl groups are connected in pairs to form fatty acids.
57
Metabolic Pool• Anabolism (cont’d): Proteins
• They are made up of combinations of 20 different amino acids.
• Some amino acids (11) can be synthesized by adult humans.
• However, other amino acids (9) cannot be synthesized by humans.
– Essential amino acids– Must be present in the diet
58
The Energy Organelles Revisited• Similarities between photosynthesis and cellular
respiration: Use of membrane
• Chloroplasts’ inner membrane forms thylakoids.• Mitochondria’s inner membranes form cristae.
Electron transport chain ETC is located on thylakoid membranes and cristae.
In photosynthesis, electrons passed to ETC were energized by the sun.
In mitochondria electrons, energized electrons were removed from glucose.
In both, ETC establishes an electrochemical gradient of H+ with ATP production by chemiosmosis.
Enzymes• In chloroplast, stroma has Calvin cycle enzymes.• In mitochondria, matrix contains enzymes of citric acid cycle. 59
Flow of Energy• Energy flows from the sun through chloroplasts to
carbohydrates and then through mitochondria to ATP molecules. This flow of energy maintains biological organization at all
levels from molecules to organisms to the biosphere. Some energy is lost with each chemical transformation.
• Eventually all solar energy captured is lost.• All life depends on solar energy input.
• Chemicals cycle within natural systems. Chloroplasts produce oxygen and carbohydrates, which are
used by mitochondria to generate energy for life.• Chloroplasts and mitochondria allow energy flow
through organisms and permit chemical cycling.60
The Energy Organelles Revisited
61
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O2
O2
enzymesgranaPhotosynthesis
NADP+
CH2O
NADPH
CO2
enzyme-catalyzedreactions
NADH
enzymes
H2O
membrane
ATP productionvia chemiosmosis
ADP ATP
H2O
membrane
Cellular RespirationNAD+
cristaeCH2O CO2